/*
Copyright (c) 2003-2006 Gino van den Bergen / Erwin Coumans  http://continuousphysics.com/Bullet/

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, 
including commercial applications, and to alter it and redistribute it freely, 
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/

#include "cbtGeometryUtil.h"

/*
  Make sure this dummy function never changes so that it
  can be used by probes that are checking whether the
  library is actually installed.
*/
extern "C"
{
	void cbtBulletMathProbe();

	void cbtBulletMathProbe() {}
}

bool cbtGeometryUtil::isPointInsidePlanes(const cbtAlignedObjectArray<cbtVector3>& planeEquations, const cbtVector3& point, cbtScalar margin)
{
	int numbrushes = planeEquations.size();
	for (int i = 0; i < numbrushes; i++)
	{
		const cbtVector3& N1 = planeEquations[i];
		cbtScalar dist = cbtScalar(N1.dot(point)) + cbtScalar(N1[3]) - margin;
		if (dist > cbtScalar(0.))
		{
			return false;
		}
	}
	return true;
}

bool cbtGeometryUtil::areVerticesBehindPlane(const cbtVector3& planeNormal, const cbtAlignedObjectArray<cbtVector3>& vertices, cbtScalar margin)
{
	int numvertices = vertices.size();
	for (int i = 0; i < numvertices; i++)
	{
		const cbtVector3& N1 = vertices[i];
		cbtScalar dist = cbtScalar(planeNormal.dot(N1)) + cbtScalar(planeNormal[3]) - margin;
		if (dist > cbtScalar(0.))
		{
			return false;
		}
	}
	return true;
}

bool notExist(const cbtVector3& planeEquation, const cbtAlignedObjectArray<cbtVector3>& planeEquations);

bool notExist(const cbtVector3& planeEquation, const cbtAlignedObjectArray<cbtVector3>& planeEquations)
{
	int numbrushes = planeEquations.size();
	for (int i = 0; i < numbrushes; i++)
	{
		const cbtVector3& N1 = planeEquations[i];
		if (planeEquation.dot(N1) > cbtScalar(0.999))
		{
			return false;
		}
	}
	return true;
}

void cbtGeometryUtil::getPlaneEquationsFromVertices(cbtAlignedObjectArray<cbtVector3>& vertices, cbtAlignedObjectArray<cbtVector3>& planeEquationsOut)
{
	const int numvertices = vertices.size();
	// brute force:
	for (int i = 0; i < numvertices; i++)
	{
		const cbtVector3& N1 = vertices[i];

		for (int j = i + 1; j < numvertices; j++)
		{
			const cbtVector3& N2 = vertices[j];

			for (int k = j + 1; k < numvertices; k++)
			{
				const cbtVector3& N3 = vertices[k];

				cbtVector3 planeEquation, edge0, edge1;
				edge0 = N2 - N1;
				edge1 = N3 - N1;
				cbtScalar normalSign = cbtScalar(1.);
				for (int ww = 0; ww < 2; ww++)
				{
					planeEquation = normalSign * edge0.cross(edge1);
					if (planeEquation.length2() > cbtScalar(0.0001))
					{
						planeEquation.normalize();
						if (notExist(planeEquation, planeEquationsOut))
						{
							planeEquation[3] = -planeEquation.dot(N1);

							//check if inside, and replace supportingVertexOut if needed
							if (areVerticesBehindPlane(planeEquation, vertices, cbtScalar(0.01)))
							{
								planeEquationsOut.push_back(planeEquation);
							}
						}
					}
					normalSign = cbtScalar(-1.);
				}
			}
		}
	}
}

void cbtGeometryUtil::getVerticesFromPlaneEquations(const cbtAlignedObjectArray<cbtVector3>& planeEquations, cbtAlignedObjectArray<cbtVector3>& verticesOut)
{
	const int numbrushes = planeEquations.size();
	// brute force:
	for (int i = 0; i < numbrushes; i++)
	{
		const cbtVector3& N1 = planeEquations[i];

		for (int j = i + 1; j < numbrushes; j++)
		{
			const cbtVector3& N2 = planeEquations[j];

			for (int k = j + 1; k < numbrushes; k++)
			{
				const cbtVector3& N3 = planeEquations[k];

				cbtVector3 n2n3;
				n2n3 = N2.cross(N3);
				cbtVector3 n3n1;
				n3n1 = N3.cross(N1);
				cbtVector3 n1n2;
				n1n2 = N1.cross(N2);

				if ((n2n3.length2() > cbtScalar(0.0001)) &&
					(n3n1.length2() > cbtScalar(0.0001)) &&
					(n1n2.length2() > cbtScalar(0.0001)))
				{
					//point P out of 3 plane equations:

					//	d1 ( N2 * N3 ) + d2 ( N3 * N1 ) + d3 ( N1 * N2 )
					//P =  -------------------------------------------------------------------------
					//   N1 . ( N2 * N3 )

					cbtScalar quotient = (N1.dot(n2n3));
					if (cbtFabs(quotient) > cbtScalar(0.000001))
					{
						quotient = cbtScalar(-1.) / quotient;
						n2n3 *= N1[3];
						n3n1 *= N2[3];
						n1n2 *= N3[3];
						cbtVector3 potentialVertex = n2n3;
						potentialVertex += n3n1;
						potentialVertex += n1n2;
						potentialVertex *= quotient;

						//check if inside, and replace supportingVertexOut if needed
						if (isPointInsidePlanes(planeEquations, potentialVertex, cbtScalar(0.01)))
						{
							verticesOut.push_back(potentialVertex);
						}
					}
				}
			}
		}
	}
}
